base::RefCounted now DCHECKs when referenced from multiple threads.

base::RefCounted now DCHECKs when referenced from multiple threads.

This will allow us to catch future violations of thread safety from
scoped_refptrs. Added a new class base::UnsafeRefCounted, which does not
do the DCHECKs (it is identical to the old RefCounted). Classes that
violate the DCHECKs have been temporarily moved over to use
UnsafeRefCounted.

BUG=469952

[noyau (Ping after 24h), 2015-03-24 09:01:20]

noyau@chromium.org changed reviewers:
+ noyau@chromium.org

[noyau (Ping after 24h), 2015-03-24 09:01:21]

https://codereview.chromium.org/1004593005/diff/20001/base/memory/ref_counted.h
File base/memory/ref_counted.h (right):

https://codereview.chromium.org/1004593005/diff/20001/base/memory/ref_counted...
base/memory/ref_counted.h:49: // DFAKE_SCOPED_LOCK_THREAD_LOCKED(add_release_);
Since your code is now doing the same thing, it's probably a good idea to remove
those two TODOs.

[Alexander Potapenko, 2015-03-24 15:01:12]

glider@chromium.org changed reviewers:
+ glider@chromium.org

[Alexander Potapenko, 2015-03-24 15:01:12]

Can you please provide a command line that shows that a particular test fails
the newly introduced check?

[Matt Giuca, 2015-04-20 01:34:45]

Closing issue, as we did not reach consensus on making it illegal to pass a
non-thread-safe RefCounted across threads. (People were in favour of doing it
carefully.)